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A229075 Primes of the form p^2 + q^2 + 21, where p and q are consecutive primes. 1
191, 311, 479, 911, 1823, 2351, 4079, 5039, 6311, 8231, 9551, 10391, 13151, 14831, 17351, 22079, 24671, 33311, 35951, 41543, 51239, 57839, 61991, 69263, 73751, 76079, 84143, 101279, 103991, 106751, 111431, 115223, 141551, 145823, 198479, 210071, 223151, 263591 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: the expression p^2+q^2+c with p and q consecutive primes and c=21 generates more primes than any other value of c in the range 1..150. Hence, c=21 is considered for this sequence.

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..5000

EXAMPLE

a(1) = 191: prime(4)^2 + prime(4+1)^2 + 21 = 191, which is prime.

MAPLE

KD:= proc() local a; a:= ithprime(n)^2+ithprime(n+1)^2+21;  if isprime(a) then RETURN(a):  fi;  end: seq(KD(), n=1..300);

MATHEMATICA

Select[Table[Prime[n]^2 + Prime[n + 1]^2 + 21, {n, 100}], PrimeQ] (* T. D. Noe, Sep 12 2013 *)

CROSSREFS

Cf. A072669, A227340.

Sequence in context: A045141 A046010 A146361 * A142806 A142086 A070831

Adjacent sequences:  A229072 A229073 A229074 * A229076 A229077 A229078

KEYWORD

nonn

AUTHOR

K. D. Bajpai, Sep 12 2013

STATUS

approved

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Last modified January 21 11:28 EST 2022. Contains 350477 sequences. (Running on oeis4.)